The goal of radiation therapy is to deliver a curative dose of radiation to the tumor while minimizing the damage to the surrounding normal tissue. Currently, tumor localization is the most significant problem in radiation delivery with respect to achieving curative radiation doses. In order to maximize the delivery dose, the tumor position must be accurately known in both space and time to hit the target during treatment where motion is important. To account for this location uncertainty, tumor dose is delivered to the volume where the tumor might be during treatment. Therefore, the treatment volume and corresponding complications increase with positioning uncertainty. The long term goal of this project is to accurately locate the real-time tumor position during radiation treatment with the following constraints necessary for increasing tumor control: (1) the tumor will be located with real-time tracking where position updates will be acquired within one second; (2) the tumor position will be described in three dimensions relative to a coordinate system defined within the treatment room with an accuracy of less than 1 mm; and (3) the detectors will be extended to ranges that are 2-3 meters or greater. The localization system proposed for this project is made of an (1) implantable, passive transmitter, (2) an external dipole antenna for energizing the transmitter, and (3) a superconducting quantum interference device (SQUID) magnetometer detection system. The energized transmitter will generate a pulsed magnetic field that will be detected by the SQUID sensors which will then be used to locate the transmitter position in real-time. This phase I work of this project will specifically address the detector system design. The goal is to construct a vector magnetometer system that will measure the magnetic field signal at a level of 0.1 pT. In order to detect these extremely low level signals, SQUID magnetometers will be used as the sensors. Even though their sensitivity is large, noise is a major problem that requires specific filtering and design in order to detect these signals. We will design the basic system from measurements and experiments conducted within this project. PUBLIC HEALTH RELEVANCE: Real-time tumor tracking in radiation therapy, with positional accuracies less than 1 mm, will guide radiation to the exact location. This will reduce complications and increase tumor control to the extent that has not been possible with existing technologies. [unreadable] [unreadable] [unreadable]